Communication receivers use interference cancellation to improve performance, such as might be measured in terms of data throughput. Interference cancellation in this respect enables successful transmission of data in instances where the transmissions likely would not be received successfully in the absence of at least some reduction in the effects of interference impinging on reception of the desired signal.
The amount or extent of interference cancellation—really, more accurately understood as interference reduction, because actual cancellation is imperfect—can be understood as a cancellation “gain”. One may express cancellation gain in terms of increased throughput or in terms of the increase seen in received signal quality, such as represented by the signal-to-noise-plus-interference ratio or SINR of the demodulated symbols obtained for a desired signal component in a received signal. Here, a “desired” signal merely indicates a signal for which transmit data is recovered and it will be understood that a received wireless communication signal in general is a composite of potentially many signals of varying strengths, e.g., one or more desired signals and one or more interfering signals.
The cancellation gain depends on a number of items, including the inherent design and sophistication of the receiver and its included interference cancellation circuitry. Conventionally, the term “cancellation efficiency” or “cancellation efficiency value” is used to denote the amount of interfering signal energy removed from a desired signal after a cancellation operation. For example, a cancellation efficiency value of 0 means that no interfering energy is removed and a cancellation efficiency value of 1 means that all interfering energy from a certain interfering stream is removed. In practice, of course, no interference cancellation process has one hundred percent efficiency.
In mathematical terms, calculation of the SINR of a certain data stream is made to depend on the cancellation efficiency of interference cancellation as applied to a signal interfering with the data stream in question. This arrangement can be expressed as follows:
      SINR    d    =            S      d                      N        0            +                        ∑                      k            ≠                          ⁢                              S            k                    ⁡                      (                          1              -                              CE                k                                      )                              where Sd and Sk are powers of the received desired and interfering signal components, respectively, before additional processing, e.g. despreading/combining. Such measurements correspond to, for example, the OFDM input signal or the chip-level signal in DS-CDMA. Further, N0 is the interference power not attributed to any signals removed using interference cancellation, d denotes the index of the data stream of interest, e.g., the desired signal, whereas k denotes the index of the signal interfering with the data stream of interest. Correspondingly, CEk denotes the cancellation efficiency for the k-th interfering signal. Note that CE is typically in range of zero to one—with zero being no cancellation and one being complete cancellation. Of course, a suboptimal design for interference cancellation processing can add more noise than is removed, resulting in a CE of less than zero.
Conventionally, the interference cancellation efficiency for a given interfering signal is estimated based on the link quality between the victim receiver and the interfering transmitter or node. Conventional processing may further consider the modulation and coding scheme or “MCS” of the interfering signal. Within this conventional framework, the cancellation efficiency is interpreted as the fraction of the interference power that is removed during the IC operation.
This simplistic approach can be embodied in a simple look-up table or “LUT” that depends only on selected parameters of the interfering signal, such as the interfering signal quality and MCS. A receiver configured to perform traditional estimation of interference cancellation efficiency would obtain or guess MCS parameters for an interfering signal and would estimate its link quality with respect to the transmitter originating the interfering signal. The conventional receiver would then use both such items of information to obtain its cancellation efficiency estimate with respect to the interfering signal. In turn, the receiver might condition certain operations on that conventional estimate. See, for example, WO 2014/004897 A1